This invention relates in general to techniques for protecting the magnetic head of a hard disk drive from shocks during transport and, and more particularly, to a method and apparatus for parking and releasing the magnetic head.
Over the past twenty years, computer technology has evolved very rapidly. One aspect of this evolution has been a progressively growing demand for increased storage capacity in memory devices, especially where the information storage medium is disposed in some form of removable cartridge. In this regard, just a little over a decade ago, the typical personal computer had a floppy disk drive which accepted floppy disk cartridges that contained 5.25xe2x80x3 disks having a storage capacity up to about 720 KB per cartridge. Not long thereafter, these devices gave way to a new generation of floppy disk drives which accepted smaller floppy disk cartridges that contained 3.5xe2x80x3 disks having higher storage capacities, up to about 1.44 MB per cartridge.
Subsequently, as the evolution continued, a further significant increase in storage capacity was realized in the industry by the introduction of a storage system having removable cartridges containing floppy-type disks with storage capacities on the order of 100 MB to 250 MB. Systems of this are commercially available under the tradename ZIP from Iomega Corporation of Roy, Utah, which is the Assignee of the present application. Thereafter, another significant increase in storage capacity was realized by the introduction of a system having removable cartridges with storage capacities on the order of 1 GB to 2 GB. Systems of this type are also available from Iomega Corporation, under the tradename JAZ. The cartridges used in this system had a hard disk in an unsealed housing, with the read/write head in the drive. These two products have each enjoyed immense commercial success. Nevertheless, the demand for still greater storage capacities in removable cartridges continues to progressively increase, such there is a current need for cartridges capable of storing 5 GB to 20 GB, or even more.
The types of removable cartridges discussed above each contain a rotatably supported storage medium within an unsealed housing. The read/write heads, with associated circuitry and support structure, are in the drive rather than in the cartridge. Significantly higher storage capacities exist in hard disk technology of the type used in non-removable hard disk drives, where the disk and head are both within a sealed housing. However, there are problems involved in attempting to carry use of this technology over to removable cartridges. This is due in part to the fact that a high-capacity hard disk is highly sensitive to environmental factors such as dust and static electricity. Consequently, in order to achieve high storage densities, the sealed housing is needed for the hard disk itself, as well as for some associated components, such as the read/write heads, which must be within the sealed housing and thus within the cartridge. Although some prior attempts have been made to use hard disk technology within a sealed housing in a removable cartridge, these attempts never resulted in a product which has had any significant level of commercial success. Instead, the types of cartridges discussed above continue to dominate the market.
Where a sealed housing has been used, the most typical prior approach was to incorporate the entire structure of a hard disk drive unit into the cartridge, such that the cartridge was not significantly different from a self-contained, standalone hard disk drive unit. In a sense, this was not a true cartridge at all, but simply a complete and self-contained hard disk drive which could be removed more easily than most from the system in which it was installed. One example of such a device is a system which was commercially available as the model P3250AR removable hard disk drive from Kalok Corporation of Sunnyvale, Calif. Another example of such a system is disclosed in Blackborow et al. U.S. Pat. No. 5,041,924. Since each cartridge in this type of system is effectively a standalone, self-contained disk drive, each cartridge is relatively heavy and expensive.
A different prior approach was to split the components of a self-contained hard disk drive into two groups, and to include one group within a sealed housing in each removable cartridge, and the other group in a drive which can removably receive one of the cartridges. Examples of this approach appear in Stollorz U.S. Pat. No. 4,359,762, Iftikar et al. U.S. Pat. No. 4,965,691, Chan U.S. Pat. No. 5,214,550, Kamo et al. U.S. Pat. No. 5,235,481, Witt et al. U.S. Pat. No. 5,317,464, and Lockhart et al. U.S. Pat. No. 5,412,522. While pre-existing products using this approach were adequate for their intended purposes, they were not satisfactory in all respects, and none of them experienced any significant commercial success.
In this regard, one consideration is that a removable cartridge with a hard disk has a much higher probability of being subjected to shocks than a hard disk drive which is permanently installed in a computer. For example, the cartridge may be inadvertently dropped onto a table or floor. Shocks of this type may be more severe and occur more frequently than the typical shocks imparted to a permanently installed drive. For a number of years, it has been a common practice to build hard disk drives with a head parking arrangement, where the magnetic head is moved to a parked position when it is not in use. In the parked position, the head is aligned with a radially inner or radially outer edge portion of the hard disk, beyond the region of the disk where information is stored. These existing head parking mechanisms often use a magnet to yieldably resist movement of the head away from the parked position.
Since the shock applied to a removable cartridge may be somewhat stronger than the shocks typically applied to a permanently installed drive, it is desirable that a removable cartridge include an arrangement which will reliably hold the magnetic head in the parked position through a relatively strong shock, and yet readily release the head when the cartridge is inserted into a drive for use. Since the cartridge will typically have the magnetic head disposed within a sealed housing, in order to protect the head and disk, it is desirable that the release of the parking mechanism occur without any need for penetration or physical disruption of the seal provided by the housing. Still another consideration is that it is desirable to provide a parking mechanism which has a minimum number of total parts, and a minimum number of movable parts.
From the foregoing, it may be appreciated that a need has arisen for a method and apparatus for effectively and efficiently parking and releasing a magnetic head associated with a hard disk, in a manner which provides a strong parking force but facilitates a simple release. According to the present invention, a method and apparatus are provided to address this need in the context of an information storage cartridge which includes a port, an information storage medium, and structure operable to transfer information between the port and the storage medium, the structure including a movably supported member capable of movement to a park position. The method and apparatus involve: generating resistance to movement of the member away from the park position when the member is in the park position; and responding to the presence of an externally induced and magnetically based influence by reducing the resistance to movement of the member.